An adsorption element having an adsorbent, as disclosed in Japanese Patent Kokai Publication No. (2001)62242, has been known in the prior art. Adsorption-side and cooling-side air passageways are divisionally formed in the adsorption element. Additionally, an inner surface of the adsorption-side air passageway is coated with adsorbent.
When air is introduced into the adsorption-side air passageway of the adsorption element, the adsorbent adsorbs water vapor contained in the air. Such water vapor adsorption by the adsorbent produces heat of adsorption by which air flowing through the adsorption-side air passageway is heated. As a result, the temperature of the air in the adsorption-side air passageway increases, thereby causing the relative humidity of the air to decrease, and the amount of water vapor that the adsorbent adsorbs will be reduced finally. To cope with this, air for cooling is made to flow through an air passageway for cooling in the adsorption element so that the amount of air dehumidification is ensured by robbing heat of adsorption.